Osteoporosis Flashcards
What is osteoporosis?
A systemic skeletal disease characterised by:
- low bone mass
- micro-architectural deterioration of bone tissue
Resulting in bone fragility and susceptibility to fracture
List the classic fracture sites associated with osteoporosis?
Hip
Wrist (Colle’s fracture)
Vertebral
What is a Colle’s fracture?
A wrist fracture, often occurs after a fall on outstretched hand
Who gets osteoporosis?
Women much more than men
People over age 50
Prevalence increases with age
What are the risk factors of osteoporosis?
SHATTERED mnemonic
S - steroid use H - hyperthyroid, hyperparathyroid A - alcohol T - thin T - testosterone, low levels E - early menopause R - renal or liver failure E - erosive inflammatory bone disease (RA) D - dietary, low calcium or diabetes
Why does menopause cause osteoporosis?
Menopause = oestrogen depletion
Oestrogen usually restrains osteoclast action
No oestrogen means no restraint
The osteoclasts go mad and resorb more bone than they should
Osteoblasts can’t keep up with the osteoclasts
Net loss of bone
Why does inflammatory disease like RA cause osteoporosis?
Pro-inflammatory cytokines increase bone resorption
What endocrine diseases cause osteoporosis?
Hyperthyroidism + hyperparathyroidism
Thyroid and parathyroid hormone increase bone turnover
Cushing’s
Cortisol increased bone resorption AND induces osteoblast apoptosis
What causes decreased skeletal loading?
Lower weight
Immobility
Which drugs increase the risk of osteoporosis?
Steroids
Depo-Provera: a contraceptive
Aromatase inhibitors
Androgen deprivation
How do steroids increase the risk of osteoporosis?
Interfere with osteoblasts making them slower at making new bone
Interfere with body’s handling of calcium
What 3 things contribute to bone strength?
- Bone mineral density
- Bone size
- Bone quality
What 3 things contribute to bone quality?
- Bone turnover (clasts + blasts)
- Architecture
- Mineralisation
What is meant by ‘quiescence’ in the context of bones?
Stability, an equal balance between bone resorption and formation
What do osteoblasts do?
Form new bone
What do osteoclasts do?
Resorption (digestion) of bone
What happens to the trabeculae in osteoporosis?
Decrease in trabecular thickness
Loss of horizontal trabeculae
Decrease in strength of trabeculae
What is trabecular tissue?
The criss-cross network of thin extensions within bone
How is osteoporosis picked up?
Patients usually present following a fracture
They are tested for osteoporosis
Investigations of osteoporosis?
DEXA scan: looks at bone density, and from this given a T score
Blood:
- Calcium
- Phosphate
What is a DEXA scan?
Dual Energy X-ray absorptiometry
Measures how much X-ray has been lost as it travels through the bone
The more X-rays picked up on the other side, the less structure of the bone is left
Which areas should you scan in a DEXA scan?
The bones most at risk:
- hip
- spine
- distal radius
What is a T score?
A score calculated by comparing the result of the DEXA scan with the score of a gender matched young adult average
I.e. How much bone density have they lost since they were 20?
What classifications are given using the T score?
Normal
Osteopenia
Osteoporosis
Severe osteoporosis
